usbip代码解析--Driver侧--usbip_commom.c

/*
 * $Id: usbip_common.c 66 2008-04-20 13:19:42Z hirofuchi $
 *
 * Copyright (C) 2003-2008 Takahiro Hirofuchi
 *
 *
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
 * USA.
 */
/*
提供的外部接口
usbip_debug_flag 调式的flag，用来决定输入哪些调式信息
usbip_debug      用于修改和打印usbip_debug_flag值
usbip_dump_urb   用户打印urb的内容
usbip_dump_header用于打印usbip_header内容
usbip_start_threads 开启 usbip_device 的接收和发送线程
usbip_stop_threads 停止 usbip_device 的接收和发送线程
usbip_task_init    初始化usbip_task结构体
usbip_xmit         接收和发送TCP包
sockfd_to_socket   将sockfd获得对应的socket对象
usbip_pack_pdu     对pdu和urb进行解压包，即urb和pdu字段之间的相互赋值
usbip_header_correct_endian usbip_header 在网络编码和主机编码之间的转换
usbip_alloc_iso_desc_pdu   pdu中的iso的处理，完成urb和pdu之间对iso_desc的信息相互赋值
usbip_recv_iso             接收urb包中的iso_frame_desc数据
usbip_recv_xbuff           接收urb包中的缓存取数据，接收urb->transfer_buffer
*/
#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/tcp.h>
#include <linux/in.h>
#include "usbip_common.h"

/* version information */
#define DRIVER_VERSION "$Id: usbip_common.c 66 2008-04-20 13:19:42Z hirofuchi $"
#define DRIVER_AUTHOR "Takahiro Hirofuchi <hirofuchi _at_ users.sourceforge.net>"
#define DRIVER_DESC "usbip common driver"

/*-------------------------------------------------------------------------*/
/* debug routines */

#ifdef CONFIG_USB_DEBUG
unsigned long usbip_debug_flag = 0xffffffff;
#else
unsigned long usbip_debug_flag = 0;
#endif
EXPORT_SYMBOL(usbip_debug_flag);


/* FIXME */
struct device_attribute dev_attr_usbip_debug;
EXPORT_SYMBOL(dev_attr_usbip_debug);


static ssize_t show_flag(struct device *dev, struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%lx\n", usbip_debug_flag);
}

static ssize_t store_flag(struct device *dev, struct device_attribute *attr,
		const char *buf, size_t count)
{
	unsigned long flag;

	sscanf(buf, "%lx", &flag);
	usbip_debug_flag = flag;

	return count;
}
DEVICE_ATTR(usbip_debug, (S_IRUGO | S_IWUSR), show_flag, store_flag);

static void usbip_dump_buffer(char *buff, int bufflen)
{
}

static void usbip_dump_pipe(unsigned int p)
{
}

static void usbip_dump_usb_device(struct usb_device *dev)
{

}

static void usbip_dump_request_type(__u8 rt)
{
}

static void usbip_dump_usb_ctrlrequest(struct usb_ctrlrequest *cmd)
{
}

void usbip_dump_urb (struct urb *purb)
{
}
EXPORT_SYMBOL(usbip_dump_urb);

void usbip_dump_header(struct usbip_header *pdu)
{
}
EXPORT_SYMBOL(usbip_dump_header);


/*-------------------------------------------------------------------------*/
/* thread routines */

//param为usbip_task
//将进程后台化，允许信号SIGKILL，将当前进程赋予ut->thread，执行
//usbip_task中loop函数，并complete(ut->thread_done)，通知ut已经完成启动
//等待loop函数因返回结束，complete_and_exit（ut->thread_done）
int usbip_thread(void *param)
{
	struct usbip_task *ut = (struct usbip_task *) param;

	if (!ut)
		return -EINVAL;

	lock_kernel();//禁止内核的调度
	daemonize(ut->name);//进程后台化
	allow_signal(SIGKILL);//允许SIGKILL信号的捕捉
	ut->thread = current;//对ut->thread进行复制，保存当前进行
	unlock_kernel();//解禁内核的调度

	/* srv.rb must wait for rx_thread starting */
	complete(&ut->thread_done);//通知执行完成

	/* start of while loop */
	ut->loop_ops(ut);

	/* end of loop */
	ut->thread = NULL;

	complete_and_exit(&ut->thread_done, 0);//通知usbip_stop_threads中对应的tcp_rx和tcp_tx
}

//参数usbip_device
//启动ud->tcp_rx和ur-tcp_tx这两个接收和发送独立线程，并等待usbip_thread的complete信号
void usbip_start_threads(struct usbip_device *ud)
{
	/*
	 * threads are invoked per one device (per one connection).
	 */
	kernel_thread((int(*)(void *))usbip_thread, (void *)&ud->tcp_rx, 0);
	kernel_thread((int(*)(void *))usbip_thread, (void *)&ud->tcp_tx, 0);

	/* confirm threads are starting */
	wait_for_completion(&ud->tcp_rx.thread_done);
	wait_for_completion(&ud->tcp_tx.thread_done);
}
EXPORT_SYMBOL(usbip_start_threads);


//参数usbip_device
//停止接收和发送两个线程
void usbip_stop_threads(struct usbip_device *ud)
{
        /* kill threads related to this sdev, if v.c. exists */
	if (ud->tcp_rx.thread != NULL) {
		send_sig(SIGKILL, ud->tcp_rx.thread, 1);
		wait_for_completion(&ud->tcp_rx.thread_done);
		udbg("rx_thread for ud %p has finished\n", ud);
	}

	if (ud->tcp_tx.thread != NULL) {
		//在usbip_thread中支持allow_signal(SIGKILL)信号
		//发送SIGKILL中后，[vhci|stub]_rx_loop中的signal_pending捕获到信号，然后退出循环
		send_sig(SIGKILL, ud->tcp_tx.thread, 1);
		wait_for_completion(&ud->tcp_tx.thread_done);//与usbip_thread中的最后一行complete_and_exit对应
		udbg("tx_thread for ud %p has finished\n", ud);
	}
}
EXPORT_SYMBOL(usbip_stop_threads);

//初始化usbip_task相关属性
void usbip_task_init(struct usbip_task *ut, char *name,
		void (*loop_ops)(struct usbip_task *))
{
	ut->thread = NULL;
	init_completion(&ut->thread_done);
	ut->name = name;
	ut->loop_ops = loop_ops;
}
EXPORT_SYMBOL(usbip_task_init);


/*-------------------------------------------------------------------------*/
/* socket routines */

//接收和发送buf,接收和发送通过msg_flags来判断方向
 /*  Send/receive messages over TCP/IP. I refer drivers/block/nbd.c */
int usbip_xmit(int send, struct socket *sock, char *buf, int size, int msg_flags)
{
	int result;
	struct msghdr msg;
	struct kvec iov;
	int total = 0;

	/* for blocks of if (dbg_flag_xmit) */
	char *bp = buf;
	int osize= size;

	dbg_xmit("enter\n");

	if (!sock || !buf || !size) {
		uerr("usbip_xmit: invalid arg, sock %p buff %p size %d\n",
				sock, buf, size);
		return -EINVAL;
	}


	if (dbg_flag_xmit) {
		if (send) {
			if (!in_interrupt())
				printk(KERN_DEBUG "%-10s:", current->comm);
			else
				printk(KERN_DEBUG "interupt  :");

			printk("usbip_xmit: sending... , sock %p, buf %p, size %d, msg_flags %d\n",
					sock, buf, size, msg_flags);
			usbip_dump_buffer(buf, size);
		}
	}


	do {
		sock->sk->sk_allocation = GFP_NOIO;
		iov.iov_base    = buf;
		iov.iov_len     = size;
		msg.msg_name    = NULL;
		msg.msg_namelen = 0;
		msg.msg_control = NULL;
		msg.msg_controllen = 0;
		msg.msg_namelen    = 0;
		msg.msg_flags      = msg_flags | MSG_NOSIGNAL;

		if (send)
			result = kernel_sendmsg(sock, &msg, &iov, 1, size);
		else
			result = kernel_recvmsg(sock, &msg, &iov, 1, size, MSG_WAITALL);

		if (result <= 0) {
			udbg("usbip_xmit: %s sock %p buf %p size %u ret %d total %d\n",
					send ? "send" : "receive", sock, buf, size, result, total);
			goto err;
		}

		size -= result;
		buf += result;
		total += result;

	} while (size > 0);


	if (dbg_flag_xmit) {
		if (!send) {
			if (!in_interrupt())
				printk(KERN_DEBUG "%-10s:", current->comm);
			else
				printk(KERN_DEBUG "interupt  :");

			printk("usbip_xmit: receiving....\n");
			usbip_dump_buffer(bp, osize);
			printk("usbip_xmit: received, osize %d ret %d size %d total %d\n",
					osize, result, size, total);
		}

		if (send) {
			printk("usbip_xmit: send, total %d\n", total);
		}
	}

	return total;

err:
	return result;
}
EXPORT_SYMBOL(usbip_xmit);


//以下四个函数，现在已经移到用户空间程序处理
/* now a usrland utility should set options. */
#if 0
int setquickack(struct socket *socket)
{
	mm_segment_t oldfs;
	int val = 1;
	int ret;

	oldfs = get_fs();
	set_fs(get_ds());
	ret = socket->ops->setsockopt(socket, SOL_TCP, TCP_QUICKACK,
			(char __user *) &val, sizeof(ret));
	set_fs(oldfs);

	return ret;
}

int setnodelay(struct socket *socket)
{
	mm_segment_t oldfs;
	int val = 1;
	int ret;

	oldfs = get_fs();
	set_fs(get_ds());
	ret = socket->ops->setsockopt(socket, SOL_TCP, TCP_NODELAY,
			(char __user *) &val, sizeof(ret));
	set_fs(oldfs);

	return ret;
}

int setkeepalive(struct socket *socket)
{
	mm_segment_t oldfs;
	int val = 1;
	int ret;

	oldfs = get_fs();
	set_fs(get_ds());
	ret = socket->ops->setsockopt(socket, SOL_SOCKET, SO_KEEPALIVE,
			(char __user *) &val, sizeof(ret));
	set_fs(oldfs);

	return ret;
}

void setreuse(struct socket *socket)
{
	socket->sk->sk_reuse = 1;
}
#endif

//参数 uint sockfd
//根据sockfd,获取file对象，然后根据file对象，获取inode，调用SOCKET_I(inode)返回socke对象
struct socket *sockfd_to_socket(unsigned int sockfd)
{
	struct socket *socket;
	struct file *file;
	struct inode *inode;

	file = fget(sockfd);
	if (!file) {
		uerr("invalid sockfd\n");
		return NULL;
	}

	//获取file的inode值
	inode = file->f_dentry->d_inode;

	if (!inode || !S_ISSOCK(inode->i_mode))
		return NULL;

  //根据inode值获取socket对象
	socket = SOCKET_I(inode);

	return socket;
}
EXPORT_SYMBOL(sockfd_to_socket);



/*-------------------------------------------------------------------------*/
/* pdu routines */

//去除flags中本驱动不支持的标签，主要去除URB_NO_TRANSFER_DMA_MAP、URB_NO_SETUP_DMA_MAP
/* there may be more cases to tweak the flags. */
static unsigned int tweak_transfer_flags(unsigned int flags)
{

	if (flags & URB_NO_TRANSFER_DMA_MAP)
		/*
		 * vhci_hcd does not provide DMA-mapped I/O. The upper
		 * driver does not need to set this flag. The remote
		 * usbip.ko does not still perform DMA-mapped I/O for
		 * DMA-caplable host controllers. So, clear this flag.
		 */
		flags &= ~URB_NO_TRANSFER_DMA_MAP;

	if (flags & URB_NO_SETUP_DMA_MAP)
		flags &= ~URB_NO_SETUP_DMA_MAP;

	return flags;
}

//针对cmd命令，根据pack确定打包方向，将urb和pdu中的信息进行同步，完成相互复制
static void usbip_pack_cmd_submit(struct usbip_header *pdu, struct urb *urb, int pack)
{
	struct usbip_header_cmd_submit *spdu = &pdu->u.cmd_submit;

	/*
	 * Some members are not still implemented in usbip. I hope this issue
	 * will be discussed when usbip is ported to other operating systems.
	 */
	if (pack) {
		/* vhci_tx.c */
		spdu->transfer_flags		= tweak_transfer_flags(urb->transfer_flags);

		spdu->transfer_buffer_length	= urb->transfer_buffer_length;
		spdu->start_frame		= urb->start_frame;
		spdu->number_of_packets		= urb->number_of_packets;
		spdu->interval			= urb->interval;
	} else  {
		/* stub_rx.c */
		urb->transfer_flags         = spdu->transfer_flags;

		urb->transfer_buffer_length = spdu->transfer_buffer_length;
		urb->start_frame            = spdu->start_frame;
		urb->number_of_packets      = spdu->number_of_packets;
		urb->interval               = spdu->interval;
	}
}

//针对ret命令，根据pack确定打包方向，将urb和pdu中的信息进行同步，完成相互复制
static void usbip_pack_ret_submit(struct usbip_header *pdu, struct urb *urb, int pack)
{
	struct usbip_header_ret_submit *rpdu = &pdu->u.ret_submit;

	if (pack) {
		/* stub_tx.c */

		rpdu->status		= urb->status;
		rpdu->actual_length	= urb->actual_length;
		rpdu->start_frame	= urb->start_frame;
		rpdu->error_count	= urb->error_count;
	} else {
		/* vhci_rx.c */

		urb->status		= rpdu->status;
		urb->actual_length	= rpdu->actual_length;
		urb->start_frame	= rpdu->start_frame;
		urb->error_count	= rpdu->error_count;
	}
}

//根据cmd命令类型和pack打包方向，对pdu和urb进行打包赋值
//调用usbip_pack_cmd_submit和usbip_pack_ret_submit
void usbip_pack_pdu(struct usbip_header *pdu, struct urb *urb, int cmd, int pack)
{
	switch(cmd) {
		case USBIP_CMD_SUBMIT:
			usbip_pack_cmd_submit(pdu, urb, pack);
			break;
		case USBIP_RET_SUBMIT:
			usbip_pack_ret_submit(pdu, urb, pack);
			break;
		default:
			err("unknown command");
			/* NOTREACHED */
			//BUG();
	}
}
EXPORT_SYMBOL(usbip_pack_pdu);

//大小端编码问题，send代码转换方向
static void correct_endian_basic(struct usbip_header_basic *base, int send)
{
	if (send) {
		base->command	= cpu_to_be32(base->command);
		base->seqnum	= cpu_to_be32(base->seqnum);
		base->devid	= cpu_to_be32(base->devid);
		base->direction	= cpu_to_be32(base->direction);
		base->ep	= cpu_to_be32(base->ep);
	} else {
		base->command	= be32_to_cpu(base->command);
		base->seqnum	= be32_to_cpu(base->seqnum);
		base->devid	= be32_to_cpu(base->devid);
		base->direction	= be32_to_cpu(base->direction);
		base->ep	= be32_to_cpu(base->ep);
	}
}

static void correct_endian_cmd_submit(struct usbip_header_cmd_submit *pdu, int send)
{
	if (send) {
		pdu->transfer_flags = cpu_to_be32(pdu->transfer_flags);

		cpu_to_be32s(&pdu->transfer_buffer_length);
		cpu_to_be32s(&pdu->start_frame);
		cpu_to_be32s(&pdu->number_of_packets);
		cpu_to_be32s(&pdu->interval);
	} else {
		pdu->transfer_flags = be32_to_cpu(pdu->transfer_flags);

		be32_to_cpus(&pdu->transfer_buffer_length);
		be32_to_cpus(&pdu->start_frame);
		be32_to_cpus(&pdu->number_of_packets);
		be32_to_cpus(&pdu->interval);
	}
}

static void correct_endian_ret_submit(struct usbip_header_ret_submit *pdu, int send)
{
	if (send) {
		cpu_to_be32s(&pdu->status);
		cpu_to_be32s(&pdu->actual_length);
		cpu_to_be32s(&pdu->start_frame);
		cpu_to_be32s(&pdu->error_count);
	} else {
		be32_to_cpus(&pdu->status);
		be32_to_cpus(&pdu->actual_length);
		be32_to_cpus(&pdu->start_frame);
		be32_to_cpus(&pdu->error_count);
	}
}

static void correct_endian_cmd_unlink(struct usbip_header_cmd_unlink *pdu, int send)
{
	if (send)
		pdu->seqnum = cpu_to_be32(pdu->seqnum);
	else
		pdu->seqnum = be32_to_cpu(pdu->seqnum);
}

static void correct_endian_ret_unlink(struct usbip_header_ret_unlink *pdu, int send)
{
	if (send)
		cpu_to_be32s(&pdu->status);
	else
		be32_to_cpus(&pdu->status);
}

//对接收到的pdu进行大小端调正，send代码接收还是发送
//函数根据pdu->base.command来分别对四种pdu包进行解析
void usbip_header_correct_endian(struct usbip_header *pdu, int send)
{
	__u32 cmd = 0;

	if (send)
		cmd = pdu->base.command;

	correct_endian_basic(&pdu->base, send);

	if (!send)
		cmd = pdu->base.command;

	switch (cmd) {
		case USBIP_CMD_SUBMIT:
			correct_endian_cmd_submit(&pdu->u.cmd_submit, send);
			break;
		case USBIP_RET_SUBMIT:
			correct_endian_ret_submit(&pdu->u.ret_submit, send);
			break;

		case USBIP_CMD_UNLINK:
			correct_endian_cmd_unlink(&pdu->u.cmd_unlink, send);
			break;
		case USBIP_RET_UNLINK:
			correct_endian_ret_unlink(&pdu->u.ret_unlink, send);
			break;

		default:
			/* NOTREACHED */
			err("unknown command in pdu header: %d", cmd);
			//BUG();
	}
}
EXPORT_SYMBOL(usbip_header_correct_endian);

//根据send判断方向，来调整iso字段的大小端
static void usbip_iso_pakcet_correct_endian(struct usbip_iso_packet_descriptor *iso, int send)
{
	/* does not need all members. but copy all simply. */
	if (send) {
		iso->offset	= cpu_to_be32(iso->offset);
		iso->length	= cpu_to_be32(iso->length);
		iso->status	= cpu_to_be32(iso->status);
		iso->actual_length = cpu_to_be32(iso->actual_length);
	} else {
		iso->offset	= be32_to_cpu(iso->offset);
		iso->length	= be32_to_cpu(iso->length);
		iso->status	= be32_to_cpu(iso->status);
		iso->actual_length = be32_to_cpu(iso->actual_length);
	}
}

//根据pack判断方向，将iso和uiso的属性字段进行相互赋值
static void usbip_pack_iso(struct usbip_iso_packet_descriptor *iso,
		struct usb_iso_packet_descriptor *uiso, int pack)
{
	if (pack) {
		iso->offset		= uiso->offset;
		iso->length		= uiso->length;
		iso->status		= uiso->status;
		iso->actual_length	= uiso->actual_length;
	} else {
		uiso->offset		= iso->offset;
		uiso->length		= iso->length;
		uiso->status		= iso->status;
		uiso->actual_length	= iso->actual_length;
	}
}

//分配urb->number_of_packets个usbip_iso_packet_descriptor描述结构体
//并将urb->iso_frame_desc[0----np-1]个usb_iso_packet_descriptor写入到buff中
//将bufff返回
/* must free buffer */
void *usbip_alloc_iso_desc_pdu(struct urb *urb, ssize_t *bufflen)
{
	void *buff;
	struct usbip_iso_packet_descriptor *iso;
	int np = urb->number_of_packets;
	ssize_t size = np * sizeof(*iso);
	int i;

	buff = kzalloc(size, GFP_KERNEL);
	if (!buff)
		return NULL;

	for (i = 0; i < np; i++) {
		iso = buff + (i * sizeof(*iso));
		//对每一个usbip_iso_packet_descriptor包进行处理，保存到iso中，并调整大小端
		usbip_pack_iso(iso, &urb->iso_frame_desc[i], 1);
		usbip_iso_pakcet_correct_endian(iso, 1);
	}

	*bufflen = size;

	return buff;
}
EXPORT_SYMBOL(usbip_alloc_iso_desc_pdu);

//接收urb->number_of_packets个包，并以此对这些包进行大小端转换
/* some members of urb must be substituted before. */
int usbip_recv_iso(struct usbip_device *ud, struct urb *urb)
{
	void *buff;
	struct usbip_iso_packet_descriptor *iso;
	int np = urb->number_of_packets;
	int size = np * sizeof(*iso);
	int i;
	int ret;

	if (!usb_pipeisoc(urb->pipe))
		return 0;

	/* my Bluetooth dongle gets ISO URBs which are np = 0 */
	if (np == 0) {
		//uinfo("iso np == 0\n");
		//usbip_dump_urb(urb);
		return 0;
	}

	buff = kzalloc(size, GFP_KERNEL);
	if (!buff)
		return -ENOMEM;

	ret = usbip_xmit(0, ud->tcp_socket, buff, size, 0);
	if (ret != size) {
		uerr("recv iso_frame_descriptor, %d\n", ret);
		kfree(buff);

		if (ud->side == USBIP_STUB)
			usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
		else
			usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);

		return -EPIPE;
	}

	for (i = 0; i < np; i++) {
		iso = buff + (i * sizeof(*iso));

		usbip_iso_pakcet_correct_endian(iso, 0);
		usbip_pack_iso(iso, &urb->iso_frame_desc[i], 0);
	}


	kfree(buff);

	return ret;
}
EXPORT_SYMBOL(usbip_recv_iso);


//根据ud->side来判断urb->pipe的类型是否正确和获取接收大小，然后接收数据
//将接收的数据保存到urb->transfer_buffer
/* some members of urb must be substituted before. */
int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
{
	int ret;
	int size;

	if (ud->side == USBIP_STUB) {
		/* stub_rx.c */
		/* the direction of urb must be OUT. */
		if (usb_pipein(urb->pipe))
			return 0;

		size = urb->transfer_buffer_length;
	} else {
		/* vhci_rx.c */
		/* the direction of urb must be IN. */
		if (usb_pipeout(urb->pipe))
			return 0;

		size = urb->actual_length;
	}

	/* no need to recv xbuff */
	if (!(size > 0))
		return 0;
		
  //从接收ud->tcp_socket接收size大小的字节，保存到urb->transfer_buffer
	ret = usbip_xmit(0, ud->tcp_socket, (char *) urb->transfer_buffer, size, 0);
	if (ret != size) {
		uerr("recv xbuf, %d\n", ret);
		//当发生错误时，产生相应的事件
		if (ud->side == USBIP_STUB) {
			usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
		} else {
			usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
			return -EPIPE;
		}
	}

	return ret;
}
EXPORT_SYMBOL(usbip_recv_xbuff);


/*-------------------------------------------------------------------------*/

static int __init usbip_common_init(void)
{
	info(DRIVER_DESC "" DRIVER_VERSION);

	return 0;
}

static void __exit usbip_common_exit(void)
{
	return;
}




module_init(usbip_common_init);
module_exit(usbip_common_exit);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");